Coin validators of the prior art use mechanical, electromechanical or electrical techniques for verifying the authenticity of a coin and to assist in determining the denomination of a coin. The electrical techniques generally take the form of generating one or more magnetic fields through which the coin to be evaluated passes as it proceeds down the coin path. The disturbances in the magnetic fields caused by the coin as the coin traverses each field are evaluated.
For example, an oscillating circuit to generate the magnetic field by applying an oscillating signal to a coil can be employed. The coil as energized by the circuit is tuned to generate a magnetic field which, when a valid coin passes through it, results in significant attenuation of the amplitude of the oscillating signal. This attenuated amplitude is an indication of the authenticity of the coin and permits verification and acceptance of the coin. The coin may then be sorted according to size and therefore by denomination by either a mechanical, electrical or electromechanical sorter.
More recently, it has been proposed that a computer may be used to evaluate the tuned oscillating signals of a coil energized by an oscillating circuit to determine the authenticity and/or denomination of a coin. In general, a parameter of the oscillating signal is compared to a reference range. If the computer determines that the parameter falls within the reference range, the computer indicates that the coin is authentic and verifies it. While this system provides the ability to program the computer for various types of coins, it is not extremely accurate. First of all, such a system tends to be temperature sensitive and at extreme low or high temperatures the parameters of a valid coin may fall outside the reference range so that the system may operate inaccurately. Furthermore, it becomes difficult for the computer to distinguish between coins of similar size or mass.